Is 5361 divisible by three how do you know just by looking at it

Yes!

Step-by-step explanation:

Here is a trick. If you add up all of the numbers in the number, and if that is divisible by three, the number is divisible by three. So ...

5+3+6+1=15

15 is divisible by 3,

so 5361 is divisible by 3

(if you wanted to know, it is 1787)